Generally, in jet-propelled small-sized boats adapted to glide freely over water surface, as disclosed, e.g., in my U.S. Pat. Nos. 4,745,872 and 4,748,928, a single person rides the boat in a standing posture on the floor deck of the boat with his hands gripping the steering handle bar to rotate it for steering so as to control a steering cable extending to the stern to swing the steering nozzle of a jet-propelling device (water jet pump) installed in the stern for steering the boat.
Also mounted on the steering handle bar is a throttle operating device for controlling the opening and closing of a throttle valve for a carburetor. In a conventional throttle operating device as shown in an elevation (side view) in FIG. 20, a bracket 72 for attaching a throttle operating lever 71 to said steering handle bar 70 is made from a light metal, such as aluminum, and formed by die-casting or cutting. Extending from the lower end of the bracket 72 is a clamp piece 74 formed with a diameter reducing slit 73, while a mast piece 76 formed with a threaded hole 75 extends from the upper end of the bracket 72. And screwed into the threaded hole 75 of said mast piece 76 is a mouth piece 78 which supports the cover tube 77 of a throttle cable C.
On the other hand, the throttle operating lever 71 is triangular as seen in side view, with its relatively short side being bifurcated and its remaining long side being bent substantially into inverted U shape to form a hand rest 82 which covers the grip cover 81 of the steering handle bar 70. A locking block 83 for the throttle cable C is locked in the bent boundary between the attaching legs 80 and hand rest 82 which form an obtuse angle .alpha. therebetween. The numeral 84 denotes seats for the locking block 83, and 85 denotes a notch for insertion of the throttle cable C.
As shown in FIGS. 21 and 22, said attaching bracket 72 is fitted on the steering handle bar 70 and then fixed to the latter by a fixing bolt 86 extending transversely through the clamp piece 74, while the attaching legs 80 of the throttle operating lever 71 are joined to the bracket 72 by a pivot pin 87 inserted in the clamp piece 74 of the attaching bracket 72, said pivot pin 87 transversely extending in parallel with said fixing bolt 86, whereby the operating lever 71 can be turned to rise and fall around the axis of the pivot pin 87. Through the lever operation by hand, the throttle cable C is moved back and forth longitudinally of the boat, so that the throttle valve of the carburetor is suitably controlled for opening and closing.
With the conventional arrangement described above, however, first, the attaching bracket 72 is fitted on the steering handle bar 70; thus, when it is desired to replace the throttle operating lever 71, the operator would have to take the trouble to withdraw the grip cover 81 from the handle bar 70. This is very troublesome, obliging the operator to replace the whole handle bar 70.
Secondly, since the attaching legs 80 and hand rest 82 of the throttle operating lever 71 are bent relative to each other, forming an obtuse angle .alpha. and since the lower ends of the attaching legs 80 are joined to the clamp piece 74 extending from the lower end of the attaching bracket 72, the radius of rotation r of the operating lever 71 becomes unnecessarily long. As a result, when the operating lever 71 is fully turned to lie flat around the axis of the pivot pin 87 so as to be in close contact with the grip cover 71 of the handle bar 70 (i.e., when the throttle valve is fully opened), the throttle cable C comes in contact with the outlet of the mouth piece 78 and bends at a definite angle .theta., a fact which means that the throttle cable C cannot smoothly move back and forth in a straight line.
In that case, the throttle cable insertion guide notch 85 on the operating lever 71, as is clear from FIG. 20, opens downward and the seats 84 for the locking block 83, as shown in FIGS. 21 and 22, simply support the locking block 83 from below and open in the rear region; therefore, when the throttle cable C fails to smoothly return forward, the locking block 83 falls off the seats 84 on the operating lever 71. At any rate, severe acceleration control for the high performance engine cannot be effected.
Thirdly, since the tool for adjusting the rotation angle range of the operating lever 71 (the degree of opening of the throttle valve) is not furnished in the vicinity of the operating lever 71, it is necessary to adjust the effective length of the throttle cable C in advance at the place where it is connected to the engine; this adjustment is also a troublesome operation.
Further, because of said absence of the adjusting tool at hand, the fingers of one hand gripping the grip cover 81 on the handle bar 70 do not fit on the hand rest 82 of the operating lever 71 snugly and positively depending on the size of the operator's hand, making it difficult to apply smooth effective acceleration control.
Fourthly, since the attaching bracket 72 is made from a light metal, such as aluminum, by die-casting or cutting, it cannot be colored according to the operator's liking, nor can it be mass-produced. Further, it would rust or corrode owing to sea water. On the other hand, the throttle operating lever 71 is made from synthetic resin. However, since the hand rest 82 has an inverted U-shaped cross section, whose width dimension W is considerably large, as shown in FIG. 22, it is too large for an area to be contacted by the fingers of one hand. As a result, the fingers tend to slip off during lever operation.